Control system and control method for vehicle

ABSTRACT

A control system and a control method for a vehicle, the vehicle includes an engine, an input shaft, an output shaft, a continuously variable transmission section, a stepped transmission section and a clutch mechanism, and a control device. The continuously variable transmission section and the stepped transmission section are provided between the input shaft and the output shaft. The clutch mechanism is provided in a torque transmission path between the stepped transmission section and drive wheels. The control device is configured to disengage the clutch mechanism in a case where a vehicle speed is at least equal to a specified value and the engine is stopped.

TECHNICAL FIELD

The invention relates to a control device and a control method for avehicle that includes a clutch for connecting or blocking a torquetransmission path between a transmission gear device and drive wheels.

BACKGROUND ART

It has widely been known to configure that torque transmitted from drivewheels of a vehicle is not transmitted to a transmission gear device.For example, a vehicle that includes: an auxiliary transmissionincluding plural transmission paths with different transmission gearratios; and a clutch for connecting or blocking any of the transmissionpaths of an auxiliary transmission and a toroidal continuously variabletransmission, in a torque transmission path between the toroidalcontinuously variable transmission and drive wheels is described inJapanese Patent Application Publication No. 2002-89706 (JP 2002-89706A).

In addition, a control device described in JP 2002-89706 A is configuredto actuate the clutch at a time that an internal combustion engine as apower source is stopped, control the auxiliary transmission to a neutralposition regardless of a transmission gear step selected by a driver,and block transmission of torque between the toroidal continuouslyvariable transmission and the drive wheels. According to a configurationdescribed in JP 2002-89706 A, the transmission of the torque from thedrive wheels to the toroidal continuously variable transmission isblocked in a state where the internal combustion engine is stopped.Thus, the toroidal continuously variable transmission in an unlubricatedstate can be prevented from being actuated by the torque from the drivewheels when the vehicle is towed. Therefore, durability of the toroidalcontinuously variable transmission can be improved.

Meanwhile, in recent years, due to requests of improved fuel economy,reduced exhaust gas of vehicles, and the like, types of control referredto as so-called idle stop control, stop and start control (hereinafterdescribed as “S&S control”), and the like, which are control forstopping an internal combustion engine when the vehicle stops or aspecified condition has been established during a travel, have beenexecuted. It has been known to execute the S&S control, for example, ina case where the vehicle stops by following a traffic signal, in a casewhere depression of an accelerator pedal is cancelled by a driver and avehicle speed is reduced, in a case where the depression of theaccelerator pedal is cancelled in a state where the vehicle runs at acertain vehicle speed or higher, in a case where the driver depresses abrake pedal and the vehicle speed is thus reduced, and the like. Thatis, it is configured that, even when a main switch is in an ON state,the control for stopping the driving internal combustion engine isexecuted by establishment of the specified condition. In addition, theinternal combustion engine is temporarily stopped by the S&S control.Thus, the internal combustion engine is possibly restarted thereafter byan acceleration request or the like.

In summary, the S&S control is control for stopping fuel supply to theinternal combustion engine, stopping ignition of a gasoline engine, andthe like. Accordingly, the internal combustion engine itself can berotated under the S&S control. However, the transmission of the torquebetween the internal combustion engine and the drive wheels is blocked.It is because power is lost when the internal combustion engine isrotated during the S&S control, because drive torque fluctuatessignificantly when the internal combustion engine is restarted after anautomatic stop, because a travel state of the vehicle and an operationstate of the internal combustion engine differ when the S&S control isexecuted during the travel, and the like. For example, a clutch that isprovided on an input side of the transmission gear device is disengaged,so as to block the transmission of the torque between the internalcombustion engine and the drive wheels. The clutch only has to beprovided in the torque transmission path between the internal combustionengine and the drive wheels, and may be provided on either the inputside or an output side of the transmission gear device. In associationwith the stop of the internal combustion engine by the S&S control,various suggestions have conventionally been made for controlling theclutch.

However, it is not described in JP 2002-89706 A that the auxiliarytransmission is brought into the neutral position when the main switchis in the ON state. Thus, there is still room for improvement of thecontrol for engaging or disengaging the clutch in a state where thevehicle speed approximates zero and the internal combustion engine isstopped by bringing the auxiliary transmission into a neutral state inorder to prepare for a case where the vehicle is towed and by bringingthe auxiliary transmission into the neutral state in order to preparefor a restart of the internal combustion engine by the S&S control.

By the way, a vehicle, in which a continuously variable transmissionsection for continuously varying a transmission gear ratio and a steppedtransmission section having one or plural fixed transmission gear ratiosare provided in parallel, has been known. In this vehicle, plural torquetransmission paths that stretch from a power source to the drive wheelsare provided, and plural clutches for switching these transmission pathsare provided. The torque transmission path that stretches from the powersource to the drive wheel is configured to be switched to run throughthe transmission path including the continuously variable transmissionsection or the transmission path including the stepped transmissionsection by combinations of engaged states or disengaged states of theplural clutches. That is, it is configured to set connection or blockageof the torque transmission path, which regards to the torquetransmission path between the power source and the drive wheels, thetorque transmission path between the continuously variable transmissionsection and the power source or the drive wheels, the torquetransmission path between the stepped transmission section and the powersource or the drive wheels, and the like, by the combinations of theengaged states or the disengaged state of the plural clutches.

The configuration described in above-described JP 2002-89706 A is astructure in which the torque output from the toroidal continuouslyvariable transmission is input to the auxiliary transmission, that is, aconfiguration in which the continuously variable transmission sectionand the stepped transmission section are arranged in series.Accordingly, in the vehicle including the transmission gear device inwhich those stepped transmission section and continuously variabletransmission section are provided in parallel, there is still room forimprovement of the control for bringing the transmission gear deviceinto the neutral state by engaging or disengaging the clutches forswitching the above-described transmission path when the control forstopping the internal combustion engine is executed.

SUMMARY OF THE INVENTION

The invention has been made by paying attention to the above technicalproblem and therefore has a purpose of providing a control device and acontrol method for a vehicle, in which a transmission path including astepped transmission section and a transmission path including acontinuously variable transmission section are arranged in parallel anda clutch mechanism for switching the transmission path is provided, inorder to control actuation of a clutch mechanism in accordance with astop state or a travel state of the vehicle when an engine is stopped.

In order to achieve the above purpose, the invention is a control devicefor a vehicle that includes, between an input shaft, to which torqueoutput from an engine is input, and an output shaft for outputting thetorque: a continuously variable transmission section for continuouslyvarying a transmission gear ratio; a stepped transmission sectionprovided in parallel with the continuously variable transmission sectionand capable of setting a transmission gear ratio that cannot be set bysaid continuously variable transmission section; and a clutch mechanismprovided in a torque transmission path between the stepped transmissionsection and drive wheels, the control device characterized in that it isconfigured to disengage the clutch mechanism in a case where a vehiclespeed is at least equal to a specified value and in a case where theengine is stopped.

The invention is the control device for a vehicle characterized in that,in the above invention, it is configured to disengage the clutchmechanism in a case where the vehicle speed is lower than the specifiedvalue and in a case where the engine is stopped due to an engine stallor ignition OFF.

The invention is the control device for a vehicle characterized in that,in the above invention, it is configured to maintain engagement of theclutch mechanism in a case where the vehicle speed is lower than thespecified value and in a case where the engine is stopped due toexecution of stop and start control.

The invention is a control method for a vehicle that includes, betweenan input shaft, to which torque output from an engine is input, and anoutput shaft for outputting the torque: a continuously variabletransmission section for continuously varying a transmission gear ratio;a stepped transmission section provided in parallel with thecontinuously variable transmission section and capable of setting atransmission gear ratio that cannot be set by said continuously variabletransmission section; and a clutch mechanism provided in a torquetransmission path between the stepped transmission section and drivewheels, the control method characterized by disengaging the clutchmechanism in a case where it is determined that a vehicle speed is atleast equal to a specified value and in a case where the engine isstopped.

The invention is the control method for a vehicle in the above inventioncharacterized by disengaging the clutch mechanism in a case where it isdetermined that the vehicle speed is lower than the specified value andin a case where it is determined that the engine is stopped due to anengine stall.

The invention is the control method for a vehicle in the above inventioncharacterized by maintaining engagement of the clutch mechanism in acase where it is determined that the vehicle speed is lower than thespecified value and in a case where it is determined that the engine isstopped due to execution of stop and start control.

Accordingly, according to the invention, a disengaging operation ormaintenance of the engagement of the clutch mechanism that is providedbetween the stepped transmission section and the output shaft can becontrolled in accordance with a stop state or a travel state of thevehicle. Thus, during a travel of the vehicle, in particular, duringfree running, coasting after the engine stall, or the like, a torquetransmission path between the stepped transmission section including agear train and the output shaft can be blocked by disengaging the clutchmechanism. Accordingly, rotation of a gear mechanism that constitutesthe stepped transmission section by the output shaft can be prevented.Thus, rotation loss by the stepped transmission section can besuppressed. Furthermore, transmission of so-called reverse input torquefrom the drive wheels to the stepped transmission section can beprevented during a speed reduction. Accordingly, the steppedtransmission section that is brought into an unlubricated state by astop of the engine can be prevented from being actuated by the reverseinput torque. Thus, durability of the stepped transmission section canbe improved. Therefore, the durability of the stepped transmissionsection can be improved by reducing torque that is unnecessarily appliedto the stepped transmission section and suppressing unnecessary rotationthereof. In addition, transmission of the reverse input torque to theengine via the stepped transmission section can be prevented.

Furthermore, according to the invention, a transmission path includingthe stepped transmission section and a transmission path including acontinuously variable transmission section are provided in parallel.Accordingly, in a case where the continuously variable transmissionsection and the drive wheels are mechanically connected and the vehicleis accelerated again in a state where the vehicle speed is high to acertain degree even when the stepped transmission section ismechanically disconnected from the drive wheels, the vehicle can beaccelerated by using the transmission path including the continuouslyvariable transmission section.

In addition, for example, in the case of the engine stall or in a casewhere an ignition switch is in an OFF state, a situation where thevehicle is towed is considered. Thus, the clutch mechanism can bedisengaged to prepare for a towed state. That is, according to theinvention, it is configured to be able to set a neutral state thatincludes a state where the clutch mechanism is disengaged. Accordingly,since the engine is stopped during towing of the vehicle, application ofthe torque from the drive wheels to the stepped transmission sectionthat is brought into the unlubricated state can be prevented. Thus, thetorque that is unnecessarily applied to the stepped transmission sectioncan be reduced, and the unnecessary rotation of the stepped transmissionsection can be suppressed. Therefore, the durability of the steppedtransmission section can be improved.

Furthermore, according to the invention, in a case where the engine isstopped due to execution of the stop and start control, the engagementof the clutch mechanism can be maintained during the stop of the vehicleor during the travel at a relatively low vehicle speed. For example, ina case where the stop and start control is executed, the torquetransmission path between the stepped transmission section and theoutput shaft can continuously be connected by maintaining the engagementof the clutch mechanism. Accordingly, in a case where relatively highdrive power is required after the engine is stopped by the stop andstart control, such as a case where the vehicle is accelerated againfrom a low vehicle speed state, delayed generation of the drive power inthe drive wheels that is based on an accelerator operation amount, thevehicle speed, and the like and follows target requested power can beprevented. In addition, in a case where the transmission gear ratio bythe stepped transmission section is set to be higher than a transmissiongear ratio by the continuously variable transmission section, a torquetransmission path between the engine and the drive wheels can beswitched in accordance with the travel state or the stop state of thevehicle.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of one example of a control device for avehicle according to the invention.

FIG. 2 is a skeletal view for illustrating one example of a powertrainin which a stepped transmission section and a continuously variabletransmission section in the invention are arranged in parallel.

FIG. 3 is a flowchart of a control flow for engaging or disengaging aclutch mechanism that is provided between the stepped transmissionsection and an output shaft.

FIG. 4 is a table that collectively shows states where each clutchmechanism and a brake mechanism are engaged or disengaged in accordancewith a travel state or a stop state of the vehicle.

MODE FOR CARRYING OUT THE INVENTION

A description will hereinafter be made on the basis of a specifiedexample of the invention. A vehicle as a target of the invention isconfigured that S&S control is executed and an internal combustionengine as a power source is stopped in a case where a specifiedcondition is established during a stop or during a travel. That is, itis configured to execute the S&S control in accordance with a stop stateor a travel state when an ignition switch as a main switch of thevehicle is in an ON state. Accordingly, the control device for a vehicleaccording to the invention is configured to control actuation of adisconnect mechanism for connecting or blocking a torque transmissionpath between the internal combustion engine and drive wheels inaccordance with the travel state or the stop state of the vehicle in astate where the internal combustion engine is stopped.

Furthermore, the vehicle as the target of the invention includes atransmission gear device, in which a continuously variable transmissionsection for continuously varying a transmission gear ratio and a steppedtransmission section having one or plural specified transmission gearratios are provided in parallel, between an input shaft, to which poweroutput from the power source is input, and an output shaft foroutputting the power. In particular, the disconnect mechanism isprovided between the transmission gear device and the drive wheels inthis specified example. Accordingly, the vehicle includes: a clutchmechanism for connecting or blocking a torque transmission path betweenthe stepped transmission section and the drive wheels; and a clutchmechanism for connecting or blocking a torque transmission path betweenthe continuously variable transmission section and the drive wheels.

FIG. 1 is a block diagram for schematically showing the control devicefor a vehicle in this specified example and the vehicle in which thecontrol device is mounted. A vehicle Ve in this specified exampleincludes a transaxle 3 provided with a disconnect mechanism C forblocking a torque transmission path that stretches from an engine 2 asthe power source to drive wheels 5 integrally rotating with an axle 4.The disconnect mechanism C is constructed of the clutch mechanisms andis configured that actuation thereof is controlled by a control device1.

The control device 1 is included in an electronic control unit (ECU)that is a controller mounted in the vehicle Ve, and is configured byincluding a central processing unit (CPU), memories (a RAM and a ROM),and a microcomputer having an input/output interface as a maincomponent. In addition, it is configured that signals from varioussensors are input to the control device 1. For example, the signalsinput to the control device 1 include: an ignition signal indicatingthat an ignition switch 61 as a main switch of the vehicle Ve is in anON state (ignition ON) or an OFF state (ignition OFF); an S&S signal bywhich it can be determined that the S&S control is currently executed;and detection signals of a vehicle speed V detected by a vehicle speedsensor 62, a speed of the engine 2, a rotational speed of the axle 4, anaccelerator operation amount Acc based on an operation of an acceleratorpedal, an operation of a brake pedal, and the like.

Furthermore, the memories of the control device 1 store various types ofdata in addition to various control programs and are configured toexecute various types of computation processing. Accordingly, thecontrol device 1 is configured to execute various types of thecomputation processing on the basis of the input signals and the storeddata and to output a command signal for executing various types ofcontrol in accordance with a result of the computation processing. Inthis specified example, the control device 1 is configured to output acommand signal for controlling actuation of the disconnect mechanism Cin accordance with the travel state or the stop state of the vehicle Ve.

Here, a description will be made on one example of a powertrain providedin the vehicle Ve with reference to FIG. 2. FIG. 2 schematically showsthe torque transmission path that stretches from the engine 2 to theaxle 4 via the transaxle 3. The engine 2 is any of a gasoline engine, adiesel engine, a hydrogen gas engine, a natural gas engine, and thelike, and is the internal combustion engine that combusts fuel to outputthe power. In particular, the engine 2 is configured that a fuelconsumption amount or a fuel consumption rate is changed in accordancewith the engine speed and output torque (engine torque). In addition,the engine 2 is configured that the power to be output is controlled onthe basis of an output operation, such as the operation of theaccelerator pedal by a driver. Accordingly, the engine 2 may besubjected to drive control, such as fuel injection control, ignitioncontrol, and intake air amount adjustment control, by an electroniccontrol unit for engine control, which is not shown. For example, in acase of the travel with an emphasis on the fuel economy, the enginespeed and the engine torque are separately controlled. In addition, in acase where the engine 2 is the gasoline engine, an intake air amount iscontrolled by controlling actuation of an electronic throttle valve,which is not shown. In this way, the engine torque is controlled.Meanwhile, in a case where the engine 2 is the diesel engine, the enginetorque is controlled by a fuel injection amount.

In addition, this vehicle Ve includes a lubrication device, which is notshown, for supplying a lubricant such as oil to portions requiringlubrication. The lubrication device is a supply source of thelubrication oil and includes an oil pump for discharging the lubricationoil when being driven. The oil pump includes a pump that is configuredto be driven by torque of a crankshaft 2 a when the engine 2 is driven.Accordingly, when the engine 2 is stopped, the oil pump is stopped.Thus, an unlubricated state where the lubrication oil is not supplied tothe portions that require the lubrication due to contact of metals, suchas a gear mechanism, possibly occurs.

Furthermore, a torque converter 6 with a lockup clutch is coupled to thecrankshaft 2 a. The torque converter 6 has a conventionally widely-knownconfiguration as a fluid transmission device. A turbine runner 6 c isarranged to face a pump impeller 6 b that is integrated with a frontcover 6 a, and a stator 6 d held via a one-way clutch, which is notshown, is arranged between these pump impeller 6 b and turbine runner 6c. That is, the front cover 6 a is coupled to the crankshaft 2 a, andthe front cover 6 a and the pump impeller 6 b integrally rotate with thecrankshaft 2 a. In addition, the turbine runner 6 c is coupled to aninput shaft 7, and it is configured that the turbine runner 6 c and theinput shaft 7 integrally rotate with each other. Furthermore, a lockupclutch 6 e that integrally rotates with the turbine runner 6 c isarranged to face an inner surface of the front cover 6 a. It should benoted that the one-way clutch is provided between the stator 6 d and afixed member such as a casing.

A forward/reverse travel switching mechanism 8 is arranged on a sameaxis as the input shaft 7. The forward/reverse travel switchingmechanism 8 is a mechanism for switching between a forward travel statewhere the torque transmitted from the input shaft 7 is transmittedwithout changing a rotational direction thereof and a reverse travelstate where the torque transmitted from the input shaft 7 is transmittedby reversing the rotational direction thereof. The forward/reversetravel switching mechanism 8 is constructed of a so-called differentialmechanism in which three rotation elements exert a differential actionamong them. That is, the various differential mechanisms of this typehave conventionally been known, and any differential mechanism can beadopted for the forward/reverse travel switching mechanism in theinvention. In this specified example, as shown in FIG. 2, theforward/reverse travel switching mechanism 8 is constructed of aplanetary gear unit of a double pinion type.

More specifically, the forward/reverse travel switching mechanism 8includes: a sun gear 8 s as an outer tooth gear; a ring gear 8 r as aninner tooth gear that is coaxially arranged with the sun gear 8 s; afirst pinion gear 8P₁ that meshes with the sun gear 8 s; a second piniongear 8P₂ that meshes with the first pinion gear 8P₁ and the ring gear 8r; and a carrier 8 c that holds these pinion gears 8P₁ and 8P₂ in amanner to allow rotation and revolution thereof. The sun gear 8 s isconfigured to integrally rotate with the input shaft 7 and constitutesan input element in the planetary gear unit. In addition, a brakemechanism B for selectively stopping rotation of the ring gear 8 r isprovided. That is, the ring gear 8 r constitutes a reaction forceelement in the planetary gear unit. The brake mechanism B is providedbetween the ring gear 8 r and the fixed member such as the casing andcan be constructed of a friction-type brake or a meshing-type brake,such as a multiplate brake.

In addition, the carrier 8 c is configured to integrally rotate with adrive gear 41 of a stepped transmission section 40, which will bedescribed below, and constitutes an output element in the planetary gearunit. Furthermore, a first clutch mechanism C₁ for selectively couplingthe carrier 8 c and the sun gear 8 s is provided between the carrier 8 cand the sun gear 8 s. The first clutch mechanism C₁ is configured todirectly transmit the torque of the input shaft 7 to the carrier 8 c asthe output element. In other words, the first clutch mechanism C₁ is amechanism, actuation of which is controlled by the control device 1, andthat selectively performs transmission or blockage of the torque betweenthe input shaft 7 and the stepped transmission section 40. That is, thefirst clutch mechanism C₁ is included in the disconnect mechanism C inthe invention. For example, when the first clutch mechanism C₁ couplesthe carrier 8 c and the sun gear 8 s, the entire forward/reverse travelswitching mechanism 8, which is constructed of the planetary gear unit,rotates integrally.

In addition, the first clutch mechanism C₁ in this specified example isconstructed of a wet-type or dry-type friction clutch, with whichtransmission torque capacity is gradually increased or decreased inaccordance with an engagement force. More specifically, the first clutchmechanism C₁ includes a hydraulic actuator connected to a hydrauliccircuit, which is not shown, and is configured to be actuated bychanging hydraulic pressure of the hydraulic actuator. The engagementforce is changed by increasing or decreasing the hydraulic pressure(engagement pressure) of the first clutch mechanism C₁. Accordingly, thecontrol device 1 is configured to control a change in the transmissiontorque capacity of the first clutch mechanism C₁ by controlling a changein the hydraulic pressure. Furthermore, in the hydraulic actuator thatis provided in the first clutch mechanism C₁, a hydraulic pressurechamber may be connected to an accumulator, which is not shown. In thiscase, the first clutch mechanism C₁ is configured to be actuated whenbeing supplied with the hydraulic pressure that is accumulated in theaccumulator.

A continuously variable transmission section 10, to which the torque ofthe input shaft 7 is input, is constructed of a belt-type continuouslyvariable transmission that has conventionally been known. Thecontinuously variable transmission section 10 includes: a primary shaft9 and a secondary shaft 11 provided in parallel; a primary pulley 20 asa drive-side member that integrally rotates with the primary shaft 9; asecondary pulley 30 as a driven-side member that integrally rotates withthe secondary shaft 11; and a belt 10 a that is wound around thesepulleys 20, 30. Accordingly, each of the pulleys 20, 30 is configured tochange a winding radius of the belt 10 a to be increased or decreased bychanging a width of a groove, on which the belt 10 a is wound, to bewidened or narrowed. That is, the continuously variable transmissionsection 10 is configured to vary a transmission gear ratio by thecontinuously variable transmission section 10 in continuous and steplessmanners by changing the width of the groove, on which the belt 10 a iswound.

More specifically, the primary pulley 20 is configured to integrallyrotate with the primary shaft 9 that is coaxially arranged with theinput shaft 7, and is arranged on an opposite side of the engine 2 withthe forward/reverse travel switching mechanism 8 being interposedtherebetween in an axial direction. In this specified example, the inputshaft 7 is configured to integrally rotate with the primary shaft 9.That is, the primary shaft 9 is coupled to integrally rotate with thesun gear 8 s of the forward/reverse travel switching mechanism 8. Inaddition, the primary pulley 20 includes: a fixed sheave 21 that isintegrated with the primary shaft 9; and a movable sheave 22 that isfitted to the primary shaft 9 in a movable manner in the axial directionso as to approach or separate from the fixed sheave 21. Furthermore, athrust application mechanism 23 that applies thrust to the movablesheave 22 so as to cause movement thereof to the fixed sheave 21 side isprovided. The thrust application mechanism 23 is constructed of anelectric actuator, a hydraulic actuator, or the like and is configuredto generate the thrust that is applied to the movable sheave 22. Thethrust application mechanism 23 is arranged on a back surface side ofthe movable sheave 22, that is, on an opposite side of the fixed sheave21 with the movable sheave 22 being interposed therebetween in the axialdirection. It should be noted that, in this specified example, theprimary shaft 9 is possibly described and explained as the input shaft 7in the following description because the primary shaft 9 is configuredto integrally rotate with the input shaft 7.

Furthermore, the secondary pulley 30 is arranged such that a rotationcenter axis of the secondary pulley 30 is parallel with a rotationcenter axis of the primary pulley 20. More specifically, the secondarypulley 30 includes: a fixed sheave 31 that is integrated with thesecondary shaft 11; and a movable sheave 32 that is configured to bemovable in the axial direction with respect to the secondary shaft 11 soas to approach or separate from the fixed sheave 31. Moreover, a thrustapplication mechanism 33 that applies the thrust to the movable sheave32 so as to cause movement thereof to the fixed sheave 31 side isprovided. The thrust application mechanism 33 is constructed of a torquecam mechanism, a spring mechanism, an electric actuator, a hydraulicactuator, or the like, and is configured to generate the axial thrustthat is applied to the movable sheave 32. In addition, the thrustapplication mechanism 33 is arranged on a back surface side of themovable sheave 32 in the axial direction, that is, on an opposite sideof the fixed sheave 31 with the movable sheave 32 being interposedtherebetween. With the thrust applied from the thrust applicationmechanism 33, the movable sheave 32 is configured to generate a forcefor holding the belt 10 a between the movable sheave 32 and the fixedsheave 31. It is configured to increase a friction force between thesecondary pulley 30 and the belt 10 a by increasing the holding force.Accordingly, it is configured that, due to the friction force, thetorque of the primary pulley 20 is transmitted to the secondary pulley30 via the belt 10 a and the torque is further transmitted to thesecondary shaft 11 that integrally rotates with the secondary pulley 30.

In this specified example, a second clutch mechanism C₂ that selectivelycouples the secondary shaft 11 and an output shaft 12 is providedbetween the secondary pulley 30 and the output shaft 12. That is, thesecond clutch mechanism C₂ can selectively perform the transmission orthe blockage of the torque between the continuously variabletransmission section 10 and the output shaft 12. The second clutchmechanism C₂ is configured to directly transmit the torque of thesecondary shaft 11 to the output shaft 12. Accordingly, actuation of thesecond clutch mechanism C₂ is controlled by the control device 1, andthe second clutch mechanism C₂ is included in the disconnect mechanismin the invention.

In addition, the second clutch mechanism C₂ in this specified example isconstructed of a wet-type or dry-type friction clutch, with whichtransmission torque capacity is gradually increased or decreased inaccordance with the engagement force. More specifically, the secondclutch mechanism C₂ includes a hydraulic actuator connected to ahydraulic circuit, which is not shown, and is configured to be actuatedby changing hydraulic pressure of the hydraulic actuator. The engagementforce is changed by increasing or decreasing the hydraulic pressure (theengagement pressure) of the second clutch mechanism C₂. Accordingly, thecontrol device 1 is configured to control a change in the transmissiontorque capacity of the second clutch mechanism C₂ by controlling achange in the hydraulic pressure. It should be noted that, in thehydraulic actuator that is provided in the second clutch mechanism C₂, ahydraulic pressure chamber may be connected to an accumulator, which isnot shown. In this case, the second clutch mechanism C₂ is configured tobe actuated when being supplied with the hydraulic pressure that isaccumulated in the accumulator.

Here, a description will be made on the stepped transmission section 40that is provided between the input shaft 7 and the output shaft 12 andhas one or plural fixed transmission gear ratios. The steppedtransmission section in the invention is a speed reduction mechanism forsetting a higher fixed transmission gear ratio than a maximumtransmission gear ratio that can be set by the continuously variabletransmission section 10, or a speed increase mechanism for setting alower fixed transmission gear ratio than a minimum transmission gearratio that can be set by the continuously variable transmission section10. That is, the invention includes the stepped transmission sectioncapable of setting the fixed transmission gear ratio that cannot be setby the continuously variable transmission section 10. As shown in FIG.2, the stepped transmission section 40 of this specified example isconstructed of the speed reduction mechanism, and is provided with acounter shaft 43 for aligning a rotational direction of the drive gear41 as a rotation member on a drive side with a rotational direction of adriven gear 45 as a rotation member on a driven side between the inputshaft 7 and the output shaft 12. The drive gear 41 is configured tointegrally rotate with the carrier 8 c as the output element of theforward/reverse travel switching mechanism 8 and always meshes with acounter driven gear 42 that is provided on the counter shaft 43. Inaddition, the counter driven gear 42 is formed to have a larger diameterthan the drive gear 41. That is, the number of tooth of the counterdriven gear 42 is larger than the number of tooth of the drive gear 41.Accordingly, in a case where the torque is transmitted from the drivegear 41 toward the counter driven gear 42, it is configured to generatea speed reducing action by a first gear pair that includes the drivegear 41 and the counter driven gear 42.

In addition, the counter shaft 43 includes a counter drive gear 44 thatis formed to have a smaller diameter than the counter driven gear 42.The counter drive gear 44 always meshes with the driven gear 45 and isformed to have a smaller diameter than the driven gear 45. That is, thenumber of tooth of the counter drive gear 44 is smaller than the numberof tooth of the driven gear 45. Accordingly, in a case where the torqueis transmitted from the counter drive gear 44 toward the driven gear 45,it is configured to generate the speed reducing action by a second gearpair that includes the counter drive gear 44 and the driven gear 45. Inaddition, the driven gear 45 is fitted to an outer circumferential sideof the output shaft 12 in a manner capable of relatively rotating withthe output shaft 12, and is configured to integrally rotate with theoutput shaft 12 by being coupled thereto by a third clutch mechanism C₃,which will be described below. That is, the stepped transmission section40 is configured that the rotational direction of the drive gear 41 isaligned with a rotational direction of the output shaft 12. Accordingly,the fixed transmission gear ratio by the stepped transmission section 40has a value that is obtained by multiplying a transmission gear ratio (agear ratio) between the drive gear 41 and the counter driven gear 42 bya transmission gear ratio (a gear ratio) between the counter drive gear44 and the driven gear 45. In addition, the fixed transmission gearratio by the stepped transmission section 40, which is shown in FIG. 2,is set to have a higher value than the maximum transmission gear ratiothat can be set by the continuously variable transmission section 10.

The third clutch mechanism C₃ is provided between the steppedtransmission section 40 and the output shaft 12 and is configured toselectively couple the driven gear 45 and the output shaft 12. That is,the third clutch mechanism C₃ can selectively perform the transmissionor the blockage of the torque between the stepped transmission section40 and the output shaft 12. That is, actuation of the third clutchmechanism C₃ is controlled by the control device 1, and the third clutchmechanism C₃ is included in the disconnect mechanism in the invention.Accordingly, the first clutch mechanism C₁ that is provided on the inputshaft 7 side and the third clutch mechanism C₃ that is provided on theoutput shaft 12 side are included as the disconnect mechanism C fordisconnecting the stepped transmission section 40 from the input shaft 7or the output shaft 12.

As described above, in this specified example, the first clutchmechanism C₁ is constructed of the friction clutch. Accordingly, thethird clutch mechanism C₃ may have a configuration for switching betweentwo states of an engaged state and a disengaged state between the drivengear 45 and the output shaft 12, and the transmission torque capacitythereof does not have to have a value between 0% and 100%. For example,the third clutch mechanism C₃ can be constructed of a meshing clutchsuch as a dog clutch or a synchromesh mechanism. FIG. 2 shows an examplein which the third clutch mechanism C₃ is constructed of the synchromeshmechanism for coupling the driven gear 45 to the output shaft 12 byfitting a sleeve 53 to both of a clutch gear 55 that is configured tointegrally rotate with the driven gear 45 and a hub 51 that isconfigured to integrally rotate with the output shaft 12. That is, thethird clutch mechanism C₃ in this specified example is a rotationsynchronizing device. Accordingly, the third clutch mechanism C₃ isconfigured to set rotational speeds of the output shaft 12 as a rotationmember on a synchronizing side and the driven gear 45 as a rotationmember on a synchronized side to be equal by the friction force. Inaddition, the third clutch mechanism C₃ is configured that actuationthereof is controlled by the control device 1. More specifically, anappropriate actuator (not shown) for moving the sleeve 53 in the axialdirection is provided, and it is configured to electrically controlactuation of the actuator by the control device 1.

In addition, it is configured to output the torque from the output shaft12 to a front differential 16 as a final speed reducer via a reductiongear mechanism 14. More specifically, an output gear 13 is attached tothe output shaft 12 in a manner to integrally rotate therewith, and alarge diameter gear 14 a that meshes with this output gear 13 isattached to a reduction gear shaft 14 b. A small diameter gear 14 c isattached to this reduction gear shaft 14 b, and this small diameter gear14 c meshes with a ring gear 15 of the front differential 16. Then, thefront differential 16 is configured to transmit the torque, which istransmitted via the ring gear 15, from the right and left axles 4 to thedrive wheels 5.

The transaxle 3 that is configured as described above is configured toswitch between the transmission path including the continuously variabletransmission section 10 and the transmission path including the steppedtransmission section 40 by switching control by the control device 1.More specifically, it is configured that the torque is transmitted fromthe input shaft 7 to the output shaft 12 via the transmission pathincluding the stepped transmission section 40 in the case of a start ina forward travel direction and in the case of a reverse travel, and itis configured that the torque is transmitted from the input shaft 7 tothe output shaft 12 via the transmission path including the continuouslyvariable transmission section 10 in the case of a forward travel at thevehicle speed V that is increased to a certain degree. For example, whena drive position (a drive range) is selected by an unillustrated shiftdevice or shift lever, the control device 1 engages the first clutchmechanism C₁ with the third clutch mechanism C₃ and disengages thesecond clutch mechanism C₂ from the brake mechanism B. Furthermore, thetransaxle 3 is controlled by the control device 1 so as to be broughtinto a neutral state where the torque transmission path between theengine 2 and the drive wheels 5 is blocked. For example, the thirdclutch mechanism C₃ is disengaged or engaged in a state where the firstclutch mechanism C₁, the second clutch mechanism C₂, and the brakemechanism B are disengaged. In FIG. 4, the engaged states and thedisengaged states of each of the clutch mechanisms C₁, C₂, C₃ and thebrake mechanism B are collectively shown in a table. In addition, “ON”described in FIG. 4 indicates being engaged, and “OFF” indicates beingdisengaged. Furthermore, “ON” in a parenthesis indicates beingtransiently brought into the engaged state.

When the vehicle starts in the forward travel direction, each of theclutch mechanisms C₁, C₂, C₃ and the brake mechanism B are set as shownin FIG. 4. In this way, the travel state where the torque is transmittedfrom the input shaft 7 to the output shaft 12 via the transmission pathincluding the stepped transmission section 40 is set. More specifically,since the first clutch mechanism C₁ is engaged, the torque transmissionpath is connected between the input shaft 7 and the stepped transmissionsection 40, and the torque output by the engine 2 is transmitted to thestepped transmission section 40 via the input shaft 7 and theforward/reverse travel switching mechanism 8. Since the two rotationelements of the forward/reverse travel switching mechanism 8 are coupledby the first clutch mechanism C₁, the entire forward/reverse travelswitching mechanism 8 rotates integrally. Accordingly, theforward/reverse travel switching mechanism 8 does not generate a speedincreasing action or the speed reducing action but transmits the torqueinput from the input shaft 7 to the drive gear 41 of the steppedtransmission section 40. In addition, since the third clutch mechanismC₃ is engaged, the torque transmission path is connected between thestepped transmission section 40 and the output shaft 12, and the torqueof the input shaft 7 is transmitted to the output shaft 12 via thestepped transmission section 40. Furthermore, since the second clutchmechanism C₂ is disengaged, the disengagement prevents the transmissionof the torque between the secondary pulley 30 and the output shaft 12.It should be noted that, in a case where an acceleration request is madeduring a travel at the relatively low vehicle speed V, it may beconfigured that each of the clutch mechanisms C₁, C₂, C₃ and the brakemechanism B are set in a similar manner to the starting state shown inFIG. 4. It is because high drive power is required.

In a case where the speed is reduced in the travel state where thetorque is transmitted via the stepped transmission section 40, thesecond clutch mechanism C₂ is disengaged, and thus the transmission ofthe torque between the output shaft 12 and the secondary pulley 30 isblocked. Accordingly, while so-called reverse input torque acts from thedrive wheels 5 to the output shaft 12, the reverse input torque does notact on the secondary pulley 30. That is, the torque from the drivewheels 5 is not applied to the continuously variable transmissionsection 10. As a result, the torque that is unnecessarily applied to thecontinuously variable transmission section 10 is reduced, and theunnecessary rotation thereof is suppressed. Thus, durability of thecontinuously variable transmission section 10 can be improved.

In a case where the vehicle speed V is increased to a predeterminedspecified vehicle speed V₁ after the vehicle starts in the forwardtravel direction, the control device 1 controls to switch from thetravel state where the torque is transmitted via the transmission pathincluding the stepped transmission section 40 to the travel state wherethe torque is transmitted via the transmission path including thecontinuously variable transmission section 10. For example, in a statewhere the transmission gear ratio by the continuously variabletransmission section 10 is set to the maximum transmission gear ratio ora transmission gear ratio near the maximum transmission gear ratio, theengaged first clutch mechanism C₁ is disengaged, and the disengagedsecond clutch mechanism C₂ is engaged. More specifically, since thefirst clutch mechanism C₁ is further disengaged in a state where thebrake mechanism B is disengaged, the forward/reverse travel switchingmechanism 8 is brought into a so-called freely rotating state. As aresult, the coupling between the input shaft 7 and the steppedtransmission section 40 is cancelled. Meanwhile, since the second clutchmechanism C₂ is engaged, the secondary pulley 30 is coupled to theoutput shaft 12. Just as described, it is configured that the torque ofthe input shaft 7 is transmitted to the output shaft 12 via thecontinuously variable transmission section 10. In addition, in thetravel state where the torque is transmitted via the transmission pathincluding the continuously variable transmission section 10, thetransmission gear ratio by the continuously variable transmissionsection 10 is gradually lowered, or the transmission gear ratio therebyis varied in accordance with the vehicle speed V and the acceleratoroperation amount Acc. In this way, the engine speed can be set to aspeed with the excellent fuel economy.

In a case where a torque transmission state via the stepped transmissionsection 40 is switched to a torque transmission state via thecontinuously variable transmission section 10, just as described, thetransmission gear ratio by the stepped transmission section 40 is higherthan the maximum transmission gear ratio by the continuously variabletransmission section 10. Thus, the transmission gear ratio or the drivepower is changed. For this reason, in a case where the first clutchmechanism C₁ is disengaged and the second clutch mechanism C₂ isengaged, the control device 1 is configured to transiently execute slipcontrol of these clutch mechanisms C₁, C₂. More specifically, engagementpressure of the second clutch mechanism C₂ is gradually increased so asto gradually increase the transmission torque capacity thereof, and inconjunction with this, engagement pressure of the first clutch mechanismC₁ is gradually decreased so as to gradually reduce the transmissiontorque capacity of the first clutch mechanism C₁. This control iscontrol that has conventionally been known as clutch-to-clutch control.The torque of the output shaft 12 is smoothly changed by theconfiguration just as described. Thus, it is possible to avoid orsuppress generation of a gear shift shock or a sense of discomfort.

Then, it may be configured that the third clutch mechanism C₃ isdisengaged after the first clutch mechanism C₁ is completely disengaged,the second clutch mechanism C₂ is completely engaged, and thus a statewhere the torque is stably transmitted via the continuously variabletransmission section 10 is set. In the travel state where thecontinuously variable transmission section 10 is used, the first clutchmechanism C₁ has already been disengaged, and thus the torque from theinput shaft 7 is not applied to the stepped transmission section 40.Accordingly, the third clutch mechanism C₃ that is constructed of themeshing clutch can be disengaged. In other words, in the case of theforward travel by using the continuously variable transmission section10, the third clutch mechanism C₃ may be in the engaged state or in thedisengaged state. Thus, in a case where the torque is transmitted viathe continuously variable transmission section 10, the control device 1is configured to control an engaging operation or a disengagingoperation of the third clutch mechanism C₃ in accordance with the travelstate, such as a case where a specified condition is established.

For example, in a case where the third clutch mechanism C₃ is disengagedduring the travel by using the continuously variable transmissionsection 10, the stepped transmission section 40 is disconnected from theinput shaft 7 and the output shaft 12. As a result, the output shaft 12does not cause the rotation of the stepped transmission section 40.Accordingly, power loss by the stepped transmission section 40 can bereduced, and deterioration of durability of the stepped transmissionsection 40 can be suppressed. Furthermore, noise and a vibration thatare generated by the rotation of the stepped transmission section 40 canbe suppressed. In addition, the torque from the input shaft 7 istransmitted to the sun gear 8 s in the forward/reverse travel switchingmechanism 8. At this time, the ring gear 8 r and the carrier 8 c are inthe freely rotating state. Accordingly, a difference in rotational speedamong the rotation elements is decreased due to the integral rotation asa whole and the like. Thus, power loss and deterioration of durabilityof the forward/reverse travel switching mechanism 8, or generation ofnoise or a vibration thereby can be suppressed.

In addition, in the case of the reverse travel, the travel state wherethe torque is transmitted via the stepped transmission section 40 isset. As shown in FIG. 4, the first clutch mechanism C₁ and the secondclutch mechanism C₂ are disengaged, and the third clutch mechanism C₃and the brake mechanism B are engaged. In this case, since the torquefrom the engine 2 is input to the sun gear 8 s in a state where the ringgear 8 r is fixed by the brake mechanism B in the forward/reverse travelswitching mechanism 8, the carrier 8 c rotates in the opposite directionwith respect to the sun gear 8 s. Accordingly, the torque is transmittedfrom the input shaft 7 to the output shaft 12 via the steppedtransmission section 40, and the output shaft 12 rotates in a directionto produce the reverse travel.

Furthermore, the control device 1 is configured to be able to set theneutral state by controlling the actuation of each of the clutchmechanisms C₁, C₂, C₃ and the brake mechanism B. That is, the neutralstate only has to be a state where the torque transmission path betweenthe engine 2 and the drive wheels 5 is blocked. In this specifiedexample, since the continuously variable transmission section 10 and thestepped transmission section 40 are provided in parallel between theinput shaft 7 and the output shaft 12, a neutral state includes a statewhere the transmission of the torque between the continuously variabletransmission section 10 and the output shaft 12 is blocked and thetransmission of the torque between at least one rotational shaft of theinput shaft 7 and the output shaft 12 and the stepped transmissionsection 40 is blocked. That is, the neutral state can be set bycombinations of the disengaged states and the engaged states of each ofthe clutch mechanisms C₁, C₂, C₃ and the brake mechanism B. Combinationexamples for setting the neutral state are shown in FIG. 4.

As shown in FIG. 4, a first neutral state is set by disengaging each ofthe clutch mechanisms C₁, C₂, C₃ and the brake mechanism B. That is, inthe first neutral state, the transmission of the torque between theinput shaft 7 and the stepped transmission section 40 is blocked, andthe transmission of the torque between the continuously variabletransmission section 10 and the stepped transmission section 40 isblocked. Accordingly, neither the torque output from the engine 2 northe torque from the drive wheels 5 is transmitted to the steppedtransmission section 40.

A second neutral state is set by disengaging the first and second clutchmechanisms C₁, C₂ and the brake mechanism B and engaging the thirdclutch mechanism C₃. Accordingly, while being decoupled from the inputshaft 7, the stepped transmission section 40 is coupled to the outputshaft 12. That is, in the second neutral state, in the transmission pathincluding the stepped transmission section 40, the torque transmissionpath between the input shaft 7 and the stepped transmission section 40is blocked, and the torque transmission path between the steppedtransmission section 40 and the output shaft 12 is connected. Forexample, in a case where the vehicle Ve is towed in the second neutralstate, the torque from the drive wheels 5 is blocked so as not to betransmitted to the input shaft 7 and the continuously variabletransmission section 10 but is transmitted to the stepped transmissionsection 40 via the engaged third clutch mechanism C₃.

A third neutral state is set by disengaging the second and third clutchmechanisms C₂, C₃ and the brake mechanism B and engaging the firstclutch mechanism C₁. Accordingly, while being decoupled from the outputshaft 12, the stepped transmission section 40 is coupled to the inputshaft 7. That is, in the third neutral state, in the transmission pathincluding the stepped transmission section 40, the torque transmissionpath between the input shaft 7 and the stepped transmission section 40is connected, and the torque transmission path between the steppedtransmission section 40 and the output shaft 12 is blocked. For example,in a case where the vehicle Ve is towed in the third neutral state, thetorque from the drive wheels 5 is not transmitted to the continuouslyvariable transmission section 10 and the stepped transmission section40.

For example, the control device 1 is configured to execute control forsetting any of the above-described neutral states when detecting thatthe ignition switch 61 as the main switch is in the OFF state (theignition OFF). More specifically, the control device 1 may be configuredto be able to execute control for setting either the first or thirdneutral state by disengaging the third clutch mechanism C₃ whendetecting that the engine 2 is stopped and the ignition switch 61 is inthe OFF state in the state where the third clutch mechanism C₃ isengaged. Alternatively, the control device 1 may be configured to beable to execute control for setting the first neutral state whendetecting that the engine 2 is stopped and the ignition switch 61 is inthe OFF state in the state where the third clutch mechanism C₃ isdisengaged.

Here, by referring to FIG. 4, a detailed description will be made on acase where a state where the transmission of the torque between at leastone of the input shaft 7 and the output shaft 12 and the steppedtransmission section 40 is blocked is only satisfied. As shown in FIG.4, in a state (a first disconnected state) where the transmission of thetorque is blocked between the stepped transmission section 40 and eachof the input shaft 7 and the output shaft 12, a state where the firstand third clutch mechanisms C₁, C₃ and the brake mechanism B aredisengaged and the second clutch mechanism C₂ is engaged or a statewhere the first and third clutch mechanisms C₁, C₃ and the brakemechanism B are disengaged and the second clutch mechanism C₂ is alsodisengaged may be set. It should be noted that “OFF” in the parenthesisdescribed in FIG. 4 indicates the mechanism may be in either the engagedstate or the disengaged state. For example, in a case where the secondclutch mechanism C₂ is engaged in the first disconnected state, thevehicle Ve can be controlled in such a travel state where the torque istransmitted via the continuously variable transmission section 10.Meanwhile, in a case where the second clutch mechanism C₂ is disengagedin the first disconnected state, the vehicle Ve is brought into asimilar state to the above-described first neutral state. Accordingly,in the first disconnected state, the rotation of the steppedtransmission section 40 that is caused by the torque of the input shaft7 and the output shaft 12 can be prevented.

As shown in FIG. 4, in a state (a second disconnected state) where thetransmission of the torque is blocked only between the steppedtransmission section 40 and the input shaft 7, a state where the firstclutch mechanism C₁ and the brake mechanism B are disengaged and thesecond and third clutch mechanisms C₂, C₃ are engaged or a state wherethe first and second clutch mechanisms C₁, C₂ and the brake mechanism Bare disengaged and the third clutch mechanism C₃ is engaged may be set.For example, in a case where the second clutch mechanism C₂ is engagedin the second disconnected state, the vehicle Ve can be controlled insuch a travel state where the torque is transmitted via the continuouslyvariable transmission section 10. In this case, since the output shaft12 and the stepped transmission section 40 are coupled in a mannercapable of transmitting the torque, the stepped transmission section 40rotates by the torque of the output shaft 12. Meanwhile, in a case wherethe second clutch mechanism C₂ is disengaged in the second disconnectedstate, the vehicle Ve is brought into a similar state to theabove-described second neutral state.

In addition, as shown in FIG. 4, in a state (a third disconnected state)where the transmission of the torque is blocked only between the steppedtransmission section 40 and the output shaft 12, a state where the thirdclutch mechanism C₃ and the brake mechanism B are disengaged and thefirst and second clutch mechanisms C₁, C₂ are engaged or a state wherethe second and third clutch mechanisms C₂, C₃ and the brake mechanism Bare disengaged and the first clutch mechanism C₁ is engaged may be set.For example, in a case where the second clutch mechanism C₂ is engagedin the third disconnected state, the vehicle Ve can be controlled insuch a travel state where the torque is transmitted via the continuouslyvariable transmission section 10. In this case, since the input shaft 7and the stepped transmission section 40 are coupled in a manner capableof transmitting the torque, the stepped transmission section 40 rotatesby the torque of the input shaft 7. Meanwhile, in a case where thesecond clutch mechanism C₂ is disengaged in the third disconnectedstate, the vehicle Ve is brought into a similar state to theabove-described third neutral state. Accordingly, the second clutchmechanism C₂ may be in either the engaged state or the disengaged statein the state where the stepped transmission section 40 is disconnectedfrom at least one rotational shaft of the input shaft 7 and the outputshaft 12.

Furthermore, the electronic control unit (ECU) is configured to executethe S&S control for stopping the engine 2 in accordance with the travelstate or the stop state of the vehicle Ve. It should be noted that thestate where the engine 2 is stopped includes a state where the engine 2does not output the drive torque. For example, a control state where theelectronic throttle valve is controlled to be closed and air intake intothe engine 2 is thereby blocked is included.

In this specified example, the control device 1 is configured to executecontrol for setting the above-described second neutral state or seconddisconnected state when executing the S&S control. The S&S control isexecuted, and the control device 1 executes the control for setting thesecond neutral state or the second disconnected state in a case where aspecified condition representing any of the following cases isestablished: for example, in a case where the vehicle Ve stops byfollowing a traffic signal; in a case where the depression of theaccelerator pedal is cancelled by the driver and the speed of thevehicle Ve is reduced; in a case where the depression of the acceleratorpedal is cancelled in a state where the vehicle Ve runs at the certainvehicle speed V or higher (hereinafter described as a free-runningstate); in a case where the driver depresses a brake pedal and the speedof the vehicle Ve is thus reduced; and the like. When the S&S control isexecuted, there is a case where the ignition switch 61 is in the ONstate and thereafter the vehicle Ve starts running or accelerates againdue to the operation by the driver. Accordingly, the control is executedfor setting the second neutral state or the second disconnected state,in which the third clutch mechanism C₃ is engaged, in order to preparefor the case of the startup or re-acceleration. In this way,responsiveness of the drive power during the startup or there-acceleration can be improved.

In addition, a cause of the stop of the engine 2 is not limited to thecase where the S&S control is executed but also includes a stop state ofthe engine 2 that is not based on an engine stop operation by thedriver, a case where control for stopping the engine 2 is executed inthe free-running state, and the like. The stop state of the engine 2that is not based on the engine stop operation includes an engine stallthat is the stop of the engine 2 unintended by the driver. Meanwhile,requested drive power that is computed on the basis of the vehicle speedV and the accelerator operation amount Acc is reduced by canceling thedepression of the accelerator pedal or the like in a case where thevehicle speed V is high to a certain degree. Accordingly, the enginestop control in the free-running state includes the control for stoppingthe engine 2 for a purpose of improving the fuel economy. That is, thecontrol for stopping the engine 2 in the travel state where the outputtorque (the drive torque) from the engine 2 is not required is included.Thus, the control device 1 is configured to be able to control theactuation of the third clutch mechanism C₃ for either the case where thecontrol is executed to set the second neutral state or the seconddisconnected state or the case where the control is executed to set thefirst or third neutral state, in accordance with the cause of the stopof the engine 2. For example, when the engine of the vehicle Ve stalls,the control is executed by the control device 1 to set the first neutralstate. That is, when the engine 2 is stopped by the engine stall, theactuation of each of the clutch mechanisms C₁, C₂, C₃ and the brakemechanism B are controlled to cause the disengagement thereof by thecontrol device 1.

As described above, each of the clutch mechanisms C₁, C₂, C₃ and thebrake mechanism B have a function of switching the torque transmissionpath between the engine 2 and the drive wheels 5, that is, both of afunction of connecting or blocking the torque transmission path betweenthe continuously variable transmission section 10 and the drive wheels 5and a function of connecting or blocking the torque transmission pathbetween the stepped transmission section 40 and the engine 2 or thedrive wheels 5. In other words, it is configured to be able to block thetorque transmission path between at least one of the continuouslyvariable transmission section 10 and the stepped transmission section 40and the drive wheels 5 by the control device 1. In view of this, oneexample in which the control device 1 controls the actuation of thethird clutch mechanism C₃ for connecting or blocking the torquetransmission path between the stepped transmission section 40 and theoutput shaft 12 in accordance with the travel state or the stop state ofthe vehicle Ve is shown in FIG. 3.

As shown in FIG. 3, the control device 1 determines whether the engine 2that has been driven is stopped (step S1). A case where the engine 2 isstopped includes a case where the engine 2 is stopped when the driveroperates the ignition switch 61 to be in the OFF state, a case where theengine 2 is stopped in the ON state of the ignition switch 61 due to theexecution of the S&S control, and a case where the engine 2 is stoppedby the engine stall. Then, if the engine 2 is driven, the processreturns, and determination processing in step S1 is repeated.

If a positive determination is made in step S1 due to the stop of theengine 2, the control device 1 determines whether the third clutchmechanism C₃ is currently engaged (step S2). For example, the controldevice 1 is configured to determine the engaged state or the disengagedstate of the third clutch mechanism C₃ by determining whether the sleeve53 in the third clutch mechanism C₃, which is constructed of the meshingclutch, is in a position at which the sleeve 53 is spline-fitted to thehub 51 and the clutch gear 55 or in a neutral position. If a negativedetermination is made in step S2 due to the disengagement of the thirdclutch mechanism C₃, the current control processing is terminated.

On the other hand, if a positive determination is made in step S2 due tothe engagement of the third clutch mechanism C₃, the control device 1determines whether the ignition switch 61 is in the OFF state (I/G—OFF)(step S3). In the processing in this step S3, for example, in a casewhere the vehicle Ve is the vehicle Ve that is activated when anignition key is inserted in a key cylinder and is rotated to a specifiedposition, the control device 1 is configured to determine whether aposition of the rotated ignition key (a key position) is a position atwhich the engine 2 is continuously driven. Alternatively, in a casewhere the vehicle Ve has a function referred to as so-called keylessentry or smart entry, the control device 1 is configured to determinewhether the ignition switch 61 as the main switch of the vehicle Ve isin the OFF state. Accordingly, the control device 1 is configured todetermine whether the ignition switch 61 is in the ON state or the OFFstate on the basis of the ignition signal. If a positive determinationis made in this step S3 due to the OFF state of the ignition switch 61,the control device 1 outputs a command signal for disengaging the thirdclutch mechanism C₃ (step S7) and terminates the current controlprocessing.

If a negative determination is made in step S3 due to the ON state ofthe ignition switch 61, the control device 1 determines whether thevehicle speed V is at most equal to a predetermined specified vehiclespeed (a reference vehicle speed) V₀ (step S4). The reference vehiclespeed V₀ includes a vehicle speed in a case where the vehicle Veperforms so-called coasting. That is, it is configured in this step S4whether the vehicle Ve travels at a relatively low vehicle speed isdetermined by the control device 1. In addition, the control device 1 isconfigured to detect the vehicle speed V, which is input from thevehicle speed sensor 62, and execute the determination processing instep S4. If the vehicle speed V is higher than the reference vehiclespeed V₀ and thus a negative determination is made in step S4, thecontrol device 1 outputs the command signal for disengaging the thirdclutch mechanism C₃ (step S7) and terminates the current controlprocessing. A case where the vehicle speed V is higher than thereference vehicle speed V₀, which is determined in step S4, includes thefree-running state. This free-running state is a state where thedepression of the accelerator pedal by the driver is cancelled, and thevehicle Ve may have to be accelerated again by the operation of thedriver thereafter. Since the vehicle speed V is a relatively highvehicle speed during the re-acceleration, the drive power that isrequired for the re-acceleration is relatively reduced. Thus, if thenegative determination is made in step S4, it may be configured tooutput a command signal for engaging the second clutch mechanism C₂ or acommand signal for maintaining the engaged state of the second clutchmechanism C₂ in addition to the output of the command signal fordisengaging the third clutch mechanism C₃. That is, it is configured toaccelerate by using the continuously variable transmission section 10during the re-acceleration from the free-running state.

If the vehicle speed V is at most equal to the reference vehicle speedV₀ and thus a positive determination is made in step S4, the controldevice 1 determines whether the cause of the stop of the engine 2 is theengine stall (step S5). That is, the control device 1 is configured todetermine whether the stop state of the engine 2 that is unintended bythe driver occurs in step S5. For example, the cause of the stop of theengine 2 includes a case where the driver intentionally stops the engine2 by operating the ignition switch 61, a case where the engine 2 isstopped due to the execution of the S&S control, or the stop state ofthe engine 2 that is unintended by the driver, that is, a case of theengine stall. For example, the control device 1 is configured to make anegative determination in step S5 when detecting the S&S signalindicating that the S&S control is currently executed and detecting thestop of the engine 2. In addition, the control device 1 is configured tomake a positive determination in step S5 when detecting the stop of theengine 2 in a case where the ignition signal indicating that theignition switch 61 is in the ON state is detected but the S&S signalindicating that the S&S control is currently executed is not detected.That is, the control device 1 may be configured that the processproceeds to step S6 in a case where the S&S signal indicating that theS&S control is currently executed is detected in this step S5 and thatthe process proceeds to step S7 in a case where the S&S signalindicating that the S&S control is currently executed is not detected.Then, if the engine 2 is stopped due to the engine stall or the S&Ssignal indicating that the S&S control is currently executed is notdetected, and thus the positive determination is made in this step S5,the control device 1 outputs the command signal for disengaging thethird clutch mechanism C₃ (step S7) and terminates the current controlprocessing.

On the other hand, if it is determined that the engine 2 is stopped dueto a cause other than the engine stall, in other words, the S&S signalindicating that the S&S control is currently executed is detected, thecontrol device 1 outputs a command signal for maintaining the engagementof the third clutch mechanism C₃ (step S6) and terminates the currentcontrol processing. A case where the negative determination is made instep S5 includes a case where the above-described S&S control isexecuted. Thus, in a case where the accelerator pedal is depressed bythe driver even when the S&S control is executed in the state where thedepression of the accelerator pedal by the driver is cancelled, thevehicle has to be started or accelerated again. Accordingly, it isconfigured to output the command signal for maintaining the engagedstate of the third clutch mechanism C₃ in order to prepare for the casewhere the vehicle Ve is started or accelerated again. That is, in a casewhere the vehicle is resumed from the S&S control and is acceleratedagain due to the depression of the accelerator pedal by the driver, itis configured to accelerate by using the stepped transmission section40. In addition, in a case where the engagement of the third clutchmechanism C₃ is maintained by this step S6, the second clutch mechanismC₂ may be in either the engaged state or the disengaged state. That is,it is configured to set the above-described second disconnected state bythe control in step S6. Furthermore, the negative determination is madein step S3. Thus, in a case where the negative determination is made instep S5, the case where the driver intentionally stops the engine 2 byoperating the ignition switch 61 is not included.

It should be noted that the control device 1 may be configured to outputthe command signal for disengaging the third clutch mechanism C₃ in thecontrol in above-described step S7, that is, output the command signalfor setting any state of the above-described first neutral state, thirdneutral state, first disconnected state, and third disconnected state.That is, in a case where the third clutch mechanism C₃ is disengaged bythe control in step S7, the second clutch mechanism C₂ may be in eitherthe disengaged state or the engaged state.

Here, a brief description will be made on a relationship between theabove-described specified example and the invention. The third clutchmechanism C₃ corresponds to the clutch mechanism in the invention. Inaddition, control means in step 6 that is described by referring to FIG.3 corresponds to engagement maintaining means, and control means in stepS7 corresponds to disengagement instructing means.

As described above, according to the control device for a vehicleaccording to the invention, it is possible to control the disengagingoperation or the maintenance of the engagement of the third clutchmechanism that is provided between the stepped transmission section andthe output shaft in accordance with the travel state or the stop stateof the vehicle. For example, during the travel of the vehicle, inparticular, during free running, coasting after the engine stall, or thelike, the torque transmission path between the stepped transmissionsection including a gear train and the output shaft can be blocked bydisengaging the third clutch mechanism. Accordingly, the rotation of thegear mechanism that constitutes the stepped transmission section by theoutput shaft can be prevented. Thus, rotation loss by the steppedtransmission section can be suppressed. Furthermore, the transmission ofthe so-called reverse input torque from the drive wheels to the steppedtransmission section can be prevented during the speed reduction.Accordingly, the stepped transmission section that is brought into theunlubricated state by the stop of the engine can be prevented from beingactuated by the reverse input torque. Thus, the durability of thestepped transmission section can be improved. That is, the durability ofthe stepped transmission section can be improved by reducing the torquethat is unnecessarily applied to the stepped transmission section andsuppressing the unnecessary rotation thereof. In addition, thetransmission of the reverse input torque to the engine via the steppedtransmission section can be prevented.

Moreover, the transmission path including the stepped transmissionsection and the transmission path including the continuously variabletransmission section are provided in parallel. Accordingly, in a casewhere the continuously variable transmission section and the drivewheels are mechanically connected and the vehicle is accelerated againin a state where the vehicle speed is high to a certain degree even whenthe stepped transmission section is mechanically disconnected from thedrive wheels, the vehicle can be accelerated by using the transmissionpath including the continuously variable transmission section.

In addition, in the case of the engine stall or in a case where theignition switch is in the OFF state, a situation where the vehicle istowed is considered. Thus, the third clutch mechanism can be disengagedto prepare for the towed state. That is, it is configured to be able toset the neutral state that includes the state where the third clutchmechanism is disengaged. Accordingly, since the engine is stopped duringtowing of the vehicle, the application of the torque from the drivewheels to the stepped transmission section that is brought into theunlubricated state can be prevented. Thus, the torque that isunnecessarily applied to the stepped transmission section can bereduced, and the unnecessary rotation of the stepped transmissionsection can be suppressed. Therefore, the durability of the steppedtransmission section can be improved.

Meanwhile, in a case where the S&S control is executed while the vehicleis stopped or while the vehicle runs at the relatively low vehiclespeed, the torque transmission path between the stepped transmissionsection and the output shaft can continuously be connected bymaintaining the engagement of the third clutch mechanism. Accordingly,the third clutch mechanism does not have to be actuated for theengagement in a case where the vehicle is accelerated again from the lowvehicle speed state or the vehicle is started after the engine isstopped by the S&S control. Thus, the responsiveness can be improved.That is, in a case where the relatively high drive power is requiredduring the start or the re-acceleration, the delayed generation of thedrive power in the drive wheels with respect to the requested power canbe prevented. In other words, the transmission gear ratio by the steppedtransmission section is set to be higher than the transmission gearratio by the continuously variable transmission section. Thus, thetorque transmission path between the engine and the drive wheels can beswitched in accordance with the travel state or the stop state of thevehicle.

It should be noted that the control device for a vehicle according tothe invention is not limited to the each above-described specifiedexample but can appropriately be modified within a scope that does notdepart from the purpose of the invention.

For example, it may be configured that the first clutch mechanism can beactuated by the hydraulic pressure of the accumulator even in a casewhere the first clutch mechanism and the second clutch mechanism, eachof which is constructed of the friction clutch, include the hydraulicactuator and the accumulator, and the engine is stopped. That is, it maybe configured that the first and second clutch mechanisms can beactuated regardless of the driven state or the stop state of the engine.

In addition, in the invention, an electronic control unit (an engineECU) for controlling the driving or the stop of the engine may beprovided, in addition to the control device in the above-describedspecified example. It may be configured that the S&S signal is inputfrom the engine ECU to the control device for a vehicle according to theinvention. As the detection signals that are input to the controldevice, the detection signals of a turbine rotational speed, an inputshaft rotational speed, a primary shaft rotational speed, a primarypulley groove width, a secondary pulley groove width, a secondary shaftrotational speed, an output shaft rotational speed, the hydraulicpressure of the first clutch mechanism, the hydraulic pressure of thesecond clutch mechanism, and the like are included. Furthermore, thesedetection signals may be input from various sensors, which are notshown, to the control device.

Moreover, the forward/reverse travel switching mechanism in theinvention can be constructed of a planetary gear unit of a single piniontype, instead of the above-described planetary gear unit of the doublepinion type. In addition, the first clutch mechanism is used tointegrate the entire forward/reverse travel switching mechanism thatperforms the differential action. Thus, as described in the eachabove-described specified example, a configuration in which the threerotation elements of the sun gear, the carrier, and the ring gear arecoupled may be adopted, instead of the configuration in which the tworotation elements of the sun gear and the carrier are coupled to eachother.

In addition, the third clutch mechanism in the invention may beconstructed of a synchromesh mechanism of a key type or a synchromeshmechanism of a cone type. That is, the third clutch mechanism only hasto be the meshing-type clutch, and may be constructed of a synchromeshmechanism of a single cone type or a synchromesh mechanism of a multicone type.

Furthermore, the stepped transmission section in the invention is notlimited to the gear mechanism that includes one transmission gear ratio(the gear ratio, the speed reduction ratio) as the fixed transmissiongear ratio, but may be a gear mechanism that has two or more of theplural fixed transmission gear ratios (the gear ratios, the speedreduction ratios) and can select and set any of these fixed transmissiongear ratios. That is, the stepped transmission section only has to beconstructed of the gear mechanism that can transmit the torque from theinput shaft to the output shaft. In the invention, since thetransmission gear ratio that cannot be set by the continuously variabletransmission section is set as the fixed transmission gear ratio by thestepped transmission section, the gear mechanism is constructed of thecombination of the gear pairs in which plural gears mesh with eachother. In other words, it only has to be configured that the gear ratioof these (the ratio of the number of tooth) becomes a highertransmission gear ratio than the maximum transmission gear ratio thatcan be set by the continuously variable transmission section.

DESCRIPTION OF THE REFERENCE NUMERALS AND SYMBOLS

-   -   1/CONTROL DEVICE (ECU)    -   2/ENGINE    -   3/TRANSAXLE    -   4/AXLE    -   5/DRIVE WHEEL    -   7/INPUT SHAFT    -   8/FORWARD/REVERSE TRAVEL SWITCHING MECHANISM    -   9/PRIMARY SHAFT    -   10/CONTINUOUSLY VARIABLE TRANSMISSION SECTION    -   10 a/BELT    -   11/OUTPUT SHAFT    -   13/OUTPUT GEAR    -   14/REDUCTION GEAR MECHANISM    -   16/FRONT DIFFERENTIAL    -   20/PRIMARY PULLEY    -   30/SECONDARY PULLEY    -   40/STEPPED TRANSMISSION SECTION    -   41/DRIVE GEAR    -   42/COUNTER DRIVEN GEAR    -   43/COUNTER SHAFT    -   44/COUNTER DRIVE GEAR    -   45/DRIVEN GEAR    -   51/HUB    -   53/SLEEVE    -   55/CLUTCH GEAR    -   61/IGNITION SWITCH    -   62/VEHICLE SPEED SENSOR    -   B/BRAKE MECHANISM    -   C/DISCONNECT MECHANISM    -   C₁/FIRST CLUTCH MECHANISM    -   C₂/SECOND CLUTCH MECHANISM    -   C₃/THIRD CLUTCH MECHANISM

What is claimed is:
 1. A control system for a vehicle, the vehicleincluding an engine, an input shaft, an output shaft, a continuouslyvariable transmission section, a stepped transmission section and aclutch mechanism, the input shaft being configured that torque outputfrom the engine is input, the output shaft being configured to outputthe torque, the continuously variable transmission section beingconfigured to continuously vary a transmission gear ratio, the steppedtransmission section being provided in parallel with the continuouslyvariable transmission section and capable of setting a transmission gearratio that cannot be set by said continuously variable transmissionsection, the continuously variable transmission section and the steppedtransmission section being provided between the input shaft and theoutput shaft, and the clutch mechanism being provided in a torquetransmission path between the stepped transmission section and drivewheels, the control system comprising: a control device configured todisengage the clutch mechanism, in a case where a vehicle speed is atleast equal to a specified value and the engine is stopped.
 2. Thecontrol system according to claim 1, wherein the control device isconfigured to disengage the clutch mechanism, in a case where thevehicle speed is lower than the specified value and the engine isstopped due to an engine stall or ignition OFF.
 3. The control systemaccording to claim 1, wherein the control device is configured tomaintain engagement of the clutch mechanism, in a case where the vehiclespeed is lower than the specified value and the engine is stopped due toexecution of stop and start control.
 4. A control method for a vehicle,the vehicle including an engine, an input shaft, an output shaft, acontinuously variable transmission section, a stepped transmissionsection, a clutch mechanism, and a control device, the input shaft beingconfigured that torque output from the engine is input, the output shaftbeing configured to output the torque, the continuously variabletransmission section being configured to continuously vary atransmission gear ratio, the stepped transmission section being providedin parallel with the continuously variable transmission section andcapable of setting a transmission gear ratio that cannot be set by thecontinuously variable transmission section, the continuously variabletransmission section and the stepped transmission section being providedbetween the input shaft and the output shaft, and the clutch mechanismbeing provided in a torque transmission path between the steppedtransmission section and drive wheels, the control method comprising:disengaging the clutch mechanism, by the control device, in a case whereit is determined that a vehicle speed is at least equal to a specifiedvalue and in a case where the engine is stopped.
 5. The control methodaccording to claim 4, wherein the clutch mechanism is disengaged by thecontrol device, in a case where the control device determines that thevehicle speed is lower than the specified value and the engine isstopped due to an engine stall.
 6. The control method according to claim4, wherein engagement of the clutch mechanism is maintained by thecontrol device, in a case where the control device determines that thevehicle speed is lower than the specified value and the engine isstopped due to execution of stop and start control.